Various photo/optical techniques have been employed to inspect the quality of moving webs. For example, PCT Application WO 84/02190 by J. Kuusi, published Jun. 7, 1984, describes a procedure and means for nondestructively measuring the distribution of filler and/or coating materials in the thickness direction of paper or cardboard. Radiation from a radio-isotope source is employed to excite characteristic X-ray radiation of a component of the material.
U.S. Pat. No. 4,456,374 issued Jun. 26, 1984 to E. Langberg describes a method and apparatus for determining the presence of absence of a coating on a substrate. The technique involves placing the substrate into optical contact with a light guide and utilizing the principle of frustrated total internal reflection. Light scattered from the coating surface is monitored to indicate the presence of a coating.
U.S. Pat. No. 4,490,618 issued Dec. 25, 1984 to P. Ciello describes an apparatus for analyzing the surface of a fibrous web, such as a paper or a textile. The apparatus includes a prism structure, one surface of which is placed in contact with the fibrous web under a predetermined pressure. A collimated light beam is directed into the prism and light reflected from the contact surface through the prism is directed to a detector. The detector senses the light reflected by the contact surface as well as the light diffracted at the contact surface to indicate the surface condition of the fibrous web.
U.S. Pat. No. 4,955,265 issued Sep. 11, 1990 to H. Nakagawa et al. describes a web cutting position control system capable of cutting a web having a print pattern thereon. The system includes a counter for counting the rotational pulses of a cutting cylinder for cutting the web is provided so as to compare the pulse count at the time of synchronizing mark detection with the reference value representing a value at the moment when the web and the cutting cylinder are in normal relative positions, and to control the relative positions of the web and the cutting cylinder to the normal relative positions by controlling the movement of a compensating roller until the two values become equal to each other.
U.S. Pat. No. 4,795,510 issued Jan. 3, 1989 to M. Wittrock et al. describes a technique for assembling a reinforcement patch of material onto the outer cover material of an absorbent article. The technique employs a knife roll and a vacuum slip anvil roll.
British Patent 1,575,140 published Sep. 17, 1980 and issued to SICK GmbH describes an electro-optical monitoring system for checking the presence of creases or other surface irregularities on a moving web of material. The monitoring apparatus directs a sharply defined light beam at a slightly skewed angle relative to a curved surface of the web. A photoelectric light detecting means detects light from the light beam to generate an output signal. The output signal changes in response to the entry of an irregularity into the light beam.
Conventional devices and techniques, such as those discussed above, have not been sufficiently effective for automatically adjusting a cutting or other separation process for producing predetermined segments of web material while keeping the parameters of the web segment within acceptance specifications. As a result, the web material may be cut at improper positions along the web length, and the resultant incorrect web segments can cause the manufactured product to be out of specification. The production line can suffer excessive downtime and reduced production efficiency.